Electrical starting clip for a model airplane engine



June 12, 1962 .1. CiWEYMOUTH 3,038,971

ELECTRICAL STARTING CLIP FOR A MODEL AIRPLANE ENGI NE Filed June-23, 1960 7o INVENTOR.

Jncx C. WtyMouTH BY W/L sou, SETTLE, MK/Jf/ (Au/ .4 TTORNEVS United States Patent 3,038,971 ELECTRICAL STARTING CLIP FOR A MODEL AHRPLANE ENGINE Jack C. Weymouth, 6123 Hix Road, Plymouth, Mich, assignor of one-half to Rudolph Horvath Filed June 23, 1960, Ser. No. 38,365 9 Claims. (Cl. 20051) The present invention relates to an electrical starting clip for a model airplane engine, and more particularly to an electrical starting clip adapted to be temporarily, but securely, attached to the glow plug of a model airplane engine.

Model airplane engines are conventionally provided with one cylinder which has a glow plug therein for igniting the fuel. The glow plug consists of a body having a threaded portion for securement to the engine. A heater element is provided within the body for supplying the igniting temperature to the fuel. The heater element will remain heated once the engine has been started as a result of the heat of combustion of the fuel. However, in order to start the engine, the heater element must be raised to operating temperature by means of electric current.

In order to facilitate this initial heating, a terminal is attached to the heater element and extends outwardly from the main glow plug body. The terminal is insulated from the glow plug body. The heater element extends between the terminal and body to form an electrical connection therebetween. A circuit may be completed through the heater element by applying one side of a power source to the terminal and the other side of the power source to the main glow plug body.

conventionally, this is accomplished by using two alligator-type clips each connected to one side of a dry cell battery. One clip is attached to the terminal and the other clip is attached to the main body of the glow plug by making contact with a portion of the airplane engine which is electrically connected to the glow plug body. Recently, improved starting clips have been provided to avoid this cumbersome method. One such clip is adapted to be side-mounted to the engine with one contact being inserted into the cooling fins of the engine and another contact being secured to the extending terminal of the plug.

Such clips have the disadvantage of being side mounted, there frequently being airplane structure which prevents such side mounting. Additionally, it has been found in practice that these clips tend to become loosened as the engine starts up as a result of engine vibration. This is undesirable because it is desired to apply current to the glow plug heater element for a time after the initial starting of the engine until the engine warms up.

According to the present invention, a starting clip is provided which may be mounted directly on top of the glow plug and which will be held securely in place even when the engine vibrates considerably.

It is, therefore, an object of the present invention to provide an electrical starting clip for a model airplane engine.

A further object is to provide a unitary starting clip which will complete a circuit through a glow plug in one operation.

Another object of the invention is to provide a starting clip which is directly mountable on top of the model airplane engine glow plug.

A further object of the invention is to provide an electrical starting clip which, when mounted on a glow plug, will not shake loose due to engine vibration but which may be easily removed without danger of damaging the engine or associated parts.

A still further object of the invention is to provide a starting clip which is universal in nature in that it may be used on model airplane engines of widely differing size.

Yet another object of the invention is to provide a starting clip which has the leads for connection to a source of current extending from a point adjacent the top of the clip whereby they will not become easily entangled with the airplane structure.

A further object is, in one embodiment, to provide a starting clip having means for readily testing a glow plug to determine whether or not the plug is operative.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIG. 1 is a side elevational view of one embodiment of the present invention showing the starting clip mounted on a model airplane engine;

FIG. 2 is an enlarged view, partly in section, of the starting clip of FIG. 1 showing the clip in operative relationship to a glow plug;

FIG. 3 is a sectional view taken substantially along the line 3-3 of FIG. 2 looking in the direction of the arrows showing the hinge structure of the clip;

FIG. 4 is a sectional view taken along the line 44 of FIG. 2 looking in the direction of the arrows showing the resilient means to hold the clip arms together;

FIG. 5 is a side elevational view of a second embodiment of the starting clip;

FlG. 6 is a sectional View taken substantially along the line 6-6 of FIG. 5 looking in the direction of the arrows; and

FIG. 7 is a bottom plan view of the clip of FIG. 6.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

The electrical starting clip of the present invention comprises gripping means which may be axially inserted onto the glow plug terminal which extends outwardly from a model airplane engine. The gripping means include an electrical contact for electrically engaging the glow plug terminal. Electrically-conductive axially-compressible spring structure is carried by the gripping means for electrically contacting a portion of the engine upon axial insertion of the gripping means onto the glow plug terminal. A circuit may thus be completed through the glow plug by connecting the gripping contact and spring structure to a source of current. The gripping means and the axially compressible spring structure, in addition to their electrical connections, also provide a good mechanical connection of the clip with the glow plug.

The embodiment of the starting clip shown in FIG. 1 comprises a pair of yieldably related arms 12, 14. The arms are pivotally connected adjacent to the upper ends thereof by means of the structure shown in FIG. 3. One arm 12 is provided with a recessed projection 16in which pivotally rides a projection 18 provided on the arm 14. The two arms are held together by means of a spring 20 which is best seen in FIG. 4. The spring 2G is positioned beneath the pivoting structure to the end that it will normally urge the lower ends of the arms to a closed position. The lower ends may be moved to an open position by compressing the finger-grip members 22, 24 provided on the upper ends of the arms.

One electrical contact is provided interiorly of the arms 12, 14. As will be noted, the arm 12 is provided with a recess 26 on the interior thereof. A metal plate 28 is secured in the recess 26 by means of a screw 30 and pin 32 provided on the arm 12. The pin 32 projects through an opening in the plate. A lip 34 is provided at the lower end of the plate 28 to grasp a glow plug as will be explained hereinafter. The other arm 14 is provided with a recess 36 adjacent the lower end thereof. A lip 38 is also provided at the bottom of the recess and is diametrically opposed to the lip 34 provided on the plate.

A coil spring 40, fabricated of an electrically conductive material, is secured to the arm 14 by means of screw 42. The upper portion of the spring is straightened at 44 and extends longitudinally along the arm 14' into engagement with the screw 42. The lower portion of the spring normally extends axially a distance beneath the lower end of the arms 12, 14. The spring 44 is insulated from the plate 28 by the arms 12, 14, which may be constructed of electrical insulating material.

Operation of the clip on a typical model airplane engine is illustrated in FIG. 1. The engine comprises an engine body 46 having cooling fins 48. The glow plug 50 is threadingly received in the upper end thereof. The plug comprises a main body 52 which makes electrical contact with the engine body, which is usually fabricated from metal. A terminal 54 is provided centrally of the body 52 and extends outwardly therefrom. A groove 56 is provided near the upper end of the terminal. The terminal is insulated from the glow plug body 52. The lower end of the terminal is provided with a heater element (not shown) which makes electrical contact with both the terminal and the body 52. The heater element is constructed of a resistance material whereby passage of a current therethrough will raise the temperature to a point where the heater will fire vaporized fuel in the engine cylinder. Once the heater element and cylinder are brought up to temperature, the heater element will glow" and continue operating Without the application of further current.

The clip is mounted in place by axially inserting it on the top of the terminal 54 with the lower ends of the arms 12, 14 spread apart. The lips 34, 38 form jaws to grasp or engage the groove 56 to form a good electrical and mechanical connection.

When the clip is mounted on the glow plug, the spring 40 extends downwardly into contact with the top of the engine body 46 to make electrical contact therewith. The spring 40 also acts to stabilize the clip and prevent it from being tipped sideways. Leads 58, 60 extend from the screws 30, 42 and are connected to a source of current shown as a battery 62. A switch 64 may be provided to control the application of current to the device. With the switch 64 closed, a circuit is completed through the glow plug. The circuit extends through the plate 28, terminal 54, heater element in the glow plug, body 52 of the glow plug, engine body 46, and spring 40.

The starting clip 10 is thus seen to have a number of advantageous features. Expandibility of the jaws and compressibility of the coil spring permits the clip to be mounted on engines of widely differing sizes. As a result of the mechanical securement comprising the engagement of the lips 34, 38 with the terminal and also the stabilizing force of the coil spring, the device is securely attached to the glow plug and will not shake off as a result of engine vibration. However, when desired, the lips 34, 38 may be moved out of engagement with the terminal to permit the clip to be moved without applying any force to the glow plug. This prevents damage to the airplane body or engine. Axial insertion of the clip on the top of the glow lug permits the clip to be used in the great majority of model airplane constructions. Frequently, there is a structure or portion of the airplane surrounding the sides of the engine which hampers the making of connections from the sides.

A second embodiment of the invention is illustrated in FIGS. 5, 6, and 7. The modified clip 66 includes a hollow elongated body 68, which may be made of two Wooden sections. Unlike the FIG. 2 embodiment, the FIG. 5 clip does not have expansible jaws at the lower end thereof. A plate 70 is provided adjacent the lower end of the body 68 and has an opening therein for insertion and engagement of the upper end of the glow plug terminal. As shown in FIG. 7, the opening comprises an enlarged portion 72 to permit insertion of the entire head of the terminal. A narrow slotted portion 74 extends from the enlarged opening. In operation, the clip 66 is shifted after the terminal has been inserted therethrough so that the slotted portion 74 will engage the groove provided adjacent the upper end of the terminal. A coil spring 76 is provided on the reduced end 67 of the body 68 and operates substantially the same as in the FIG. 2 embodiment.

Leads 78, 88 extend from hollow projection 82 for securement to a source of current. One lead 78 extends through the hollow body and is connected to an axially extended portion 84 of the plate 70 to provide current thereto. The second lead is connected to a plate 86 provided to extend axially within the hollow body but separated from the plate portion 84. Plate 86- has a tab 88 which extends through an opening in the body 68 to make electrical contact with the spring 76 to thus provide current therethrough.

Means are also provided on the clip 66 for testing a glow plug. In testing a glow plug, an electrical connection is made through the plug by applying a source of current to the terminal and a source of current to the body. The heater element of the plug, which is visible through the bottom of the plug body, will glow if the plug is in working order.

As will be noted, an opening 94 is provided in the clip body 70. A tab 92, which forms a part of the plate projection 84, extends to a point beneath the opening 90. A second tab 94, provided on the second plate 86, extends to a point approximately in line with the periphery of the opening 90. As shown in FIG. 6, a plug 96 may be tested by inserting the terminal 98 of the plug through the opening to make electrical contact with the tab 92. The circuit is completed through the plug by pressing the plug body against the tab 94. As previously mentioned, if the plug is in working order, the heater element will glow.

Having thus described my invention, I claim:

1. An electrical starting clip for a model airplane engine comprising gripping means for axial insertion onto a glow plug extending from a model airplane engine; said gripping means including an electrical contact for electrically engaging the glow plug; and an electrically-conductive axially-compressible spring structure carried by the gripping means for contacting a portion of the engine upon axial insertion of the gripping means onto the glow plug.

2. A device as claimed in claim 1 and further characterized in that the spring structure is a coil spring.

3. An electrical starting clip for a model airplane engine comprising a body member; gripping means in one end of the body for securement to the end of a glow plug extending from a model airplane engine; said gripping means including an electrical contact for electrically engaging the glow plug; electrically-conductive resilient means extending from said gripping means and insulated from said contact; said resilient means being operative to electrically engage the engine body when the gripping means is secured to the glow plug; and an electrical connection from each of the contact and resilient means securable to a source of current.

4. A device as claimed in claim 3 and further characterized in that the resilient means is a coil spring.

5. An electrical starting clip for a model airplane engine comprising a pair of yieldably related arms forming jaws for securement to the end of a glow plug extending from a model airplane engine; first resilient means urging the jaws to a closed position; an electrical contact carried by the jaws to electrically engage the glow plug; electrically-conductive axially-compressible second resilient means carried by one of the arms and extending axially outwardly from the jaws; said second resilient means being insulated from said contact and operative to electrically engage the engine body when the jaws are secured to the glow plug; and an electrical connection from each of the contact and second resilient means securable to a source of current.

6. A device as claimed in claim 5 and further characterized in that the second resilient means is a coil spring.

7. An electrical starting clip for a model airplane engine comprising a body member; a recess in one end of the body member; gripping means in the recess for securement to the end of a glow plug extending from a model airplane engine; said gripping means including an electrical contact for electrically engaging the glow plug; electricallyconductive axially-compressi=ble resilient means extending from said recessed end of the body member and insulated from said contact; said resilient means being operative to electrically engage the engine body when the gripping means is secured to the glow plug; and an electrical connection from each of the contact and resilient means securable to a source of current.

8. A device as claimed in claim 7 and further characterized in that the resilient means is a coil spring.

9. A device as claimed in claim 7 and further characterized in that a first contact is provided interiorly of the body member; said body member having an opening in the exterior thereof to permit access to said first contact; a test contact on the exterior of the body member adjacent to said opening; and an electrical connection from each of the contacts securable to a source of current whereby a glow plug may be tested by inserting one end of the plug through the opening to make electrical cont-act with said first contact and pressing the body of the glow against said second contact to thereby complete a circuit through the plug.

References Cited in the file of this patent UNITED STATES PATENTS 1,588,120 Maijgren June 8, 1926 2,040,678 Van Buskirk May 12, 1936 2,075,632 Zuokerman Mar. 1937 2,108,708 Foster Feb. 15, 1938 2,928,067 Broberg, et al Mar. 8, 1960 FOREIGN PATENTS 1,119,020 France Mar. 26, 1956 

